This invention relates to moisture vapor permeable film dressings for covering wounds on human and animal skin, and, more particularly, to a structure of a thin transparent moisture vapor permeable film dressing with a moisture vapor permeable adhesive, there being a vapor permeable non-woven fabric secured to the film on a side opposite the adhesive to facilitate manipulation of the dressing, and to provide the thin film with protection from abrasion. The dressing may include optionally a pad on the adhesive side of the film for adsorption of body exudate. The composite structure of the film and the nonwoven fabric is sufficiently thin and elastic to readily conform to the shape of a body being draped by the dressing.
The use of thin films on the order of one mil thickness, which are impermeable to liquid water but permeable to water vapor is finding increased use in the construction of surgical dressings. Such dressings may include the film with or without a gauze pad or other absorptive plus some form of backing layer to facilitate emplacement of the dressing on the wound. Occasionally, the dressing is completed by use of gauze or other fabric which covers the film so as to protect the fragile film from abrasion and/or puncture by foreign objects which may contact the patient wearing the dressing.
The use of the thin film is advantageous for a number of reasons. The film is impermeable to liquid water and to bacteria so as to form a very effective shield which protects a patient from sources of infection external to the skin. The film retains body fluids within the body at the site of the wound. The vapor permeability of the film provides a sufficient rate of water vapor transport through the film to allow the skin to breathe normally. The film has sufficient elasticity to conform to the shape of various parts of the body, even a flexible body part such as a knee or elbow. Both the film and the adhesive layer may be constructed to be transparent, such transparency permitting the physician to observe the wound area without removal of the dressing. The material of the dressing is non-allergenic. The foregoing characteristics of the dressing permit the dressing to be kept in place for significantly longer periods of time than with other non-film types of dressings, this resulting in a great convenience to both the patient and attending medical staff, and also providing for better healing in some types of breaks in the integument, incisions, or wounds and providing better cost effectiveness in medical practice due to decreased need for dressing changes.
Such moisture vapor permeable films may be made from synthetic polymers and formed by casting, extrusion or other known film-making processes. Film thickness is in a range of typically 0.5-10 mils and preferably in a range from 0.6-3 mils. The film is continuous in that it has no perforations or pores which extend through the depth of the film. Films of this type are known and generally are hydrophyllic polymeric materials through which water vapor is capable of diffusing. The films are formed of plastic material such as polyurethane or acrylate copolymers, see McCracken et al, U.S. Pat. No. 4,413,621. A suitable adhesive for securing the thin film to human skin is disclosed in Hodgson, U.S. Pat. No. 3,645,835 (now U.S. Pat. Nos. Re. 31,886 and 31,887). Generally, these films have moisture vapor transport rates between 15 and 80 grams per 100 square inches per 24 hour interval at 100.degree. Fahrenheit and 90% Relative Humidity.
In spite of the many advantages of the thin film, there are problems associated with its use. The film is too thin to be handled without some form of backing sheet or release sheet because the extreme flexibility and limpness allow the film to curl over upon itself. Furthermore, in the presence of an adhesive layer on one surface of the film, the film may stick to itself, this presenting great difficulty in applying the film to a patient. While the feature of transparency is most beneficial in allowing a physician to observe the wound, this feature is distressing to a patient who would prefer not to look at an ugly wound. The film, because of its extreme thiness, is fragile, and can readily catch on a sharp or rough object resulting in a tearing of a dressing constructed of the film.
If an attempt be made to overcome the foregoing difficulties by use of a permanent backing layer of greater stiffness and resistance to abrasion, then a further problem is introduced, namely, such backing layer would materially alter the vapor transport rate of the dressing and might not allow any vapor transport. If an opaque covering, such as a cloth bandage, be placed over the film to occlude the distressing view of the wound from the patient, then the disadvantage is introduced in that an attending physician must remove the cloth covering in order to view the wound.